1. Field of the Invention
The present invention relates to ceramic fiber furnaces.
2. Related Art Statement
Recently, ceramic fiber furnaces using ceramic fibers as their walls have been widely used in producing ceramic products, owing to their good thermal efficiency and high temperature-raising rate. An ordinary wall structure of such ceramic fiber furnaces is composed of a substrate member 12, such as steel plate, a wall of ceramic fibers 11 applied on the inner surface of the substrate member 12, a ceramic fiber board 13 applied on the inner surface of the wall of the ceramic fibers 11, and a ceramic pin 14 penetrating through the substrate member 12, the wall of the ceramic fibers 11, and the ceramic fiber boards 13 for fixing the same by means of a spring 16, as shown in FIG. 4. The ceramic pin 14 has a ceramic nut 15 threaded therewith at the inner end thereof at the inside of the ceramic fiber furnace, a spring-supporting nut 10 at the outer end thereof, and a spring 16 engaged therewith and held by the nut 10 at the outside of the ceramic fiber furnace. The spring 16 exerts an outwardly directed resilient power on the ceramic pin 14, so that the ceramic nut 15 presses the ceramic fiber board 13 outwardly from the inside of the ceramic fiber furnace.
However, the ceramic pin 14 and the ceramic nut 15 of the wall structure of the conventional ceramic fiber furnaces are expanded and deformed at high temperatures to a position as shown by the imagination line in FIG. 2, for example, and shrunk and retracted at low temperatures to their original position as shown by the solid line in FIG. 2. Therefore, the ceramic nut 15 is displaced on the surface of the ceramic fiber board 13 in contact therewith, so that minute ceramic fibers are peeled off from the surface of the ceramic fiber board 13. Particularly, such minute ceramic fibers which peeled off from the ceramic fiber board 13 are spread and adhered on the glazed surface, etc., of the fired products to cause an insufficient firing.
Therefore, in case when firing ceramic products which dislike the adhesion of the minute ceramic fibers, there are adopted such methods as, firing in a muffle furnace, firing by a reflector system, or firing in a furnace of bricks walls. However these furnaces have drawbacks in that they need a large heat source as compared with those of ceramic fiber furnaces, that heat efficiency is bad, and that the temperature-raising rate is small, etc.